As climate-change arguments continue at home — including pundits who assert the scientific consensus on the issue is overblown or concocted — current and former Department of Defense officials are mapping future strategies to protect U.S. interests in the aftermath of massive floods, water shortages and famines that are expected to hit and decimate unstable nations.

“For DoD, this is a mission reality, not a political debate,” said Mark Wright, a Pentagon spokesman. “The scientific forecast is for more Arctic ice melt, more sea-level rise, more intense storms, more flooding from storm surge, and more drought.

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But inside and outside the DoD, many experts agree U.S. national security already is being tested by massive unrest, revolts and humanitarian calamities triggered, in part, by climate change.

The civil war in Syria, which has left an estimated 100,000 people dead, has its roots in a regional drought, said retired Navy Vice Adm. Lee Gunn, now a member of the military advisory board for CNA Corporation, a non-profit research and analysis organization in Alexandria, Virginia.

TheNational Climate Assessmentis the definitive statement of current and future impacts of carbon pollution on the United States. And the picture it paints is stark: Inaction will devastate much of the arable land of the nation’s breadbasket — and ruin a livable climate for most Americans.

“Americans face choices” explains the Congressionally-mandated report by 300 leading climate scientists and experts, which was reviewed by the National Academy of Sciences. We’re already seeing serious climate impacts — such as more extreme heat waves, droughts, and deluges — and additional impacts are “now unavoidable.” But just how bad future climate change is “will still largely be determined by choices society makes about emissions.”

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One of the most dangerous consequences of that staggering rise in heat is a drop in soil moisture — basically precipitation minus evaporation — a key indicator of drought. Places that don’t see any drop in precipitation will still see a drop in soil moisture when it is hotter because of the evaporation, the drying out of the soil in the hot sun. Even worse is that much of the Southwest is projected to see less precipitation.

In a troubling new discovery, scientists studying ocean waters off California, Oregon and Washington have found the first evidence that increasing acidity in the ocean is dissolving the shells of a key species of tiny sea creature at the base of the food chain.

The animals, a type of free-floating marine snail known as pteropods, are an important food source for salmon, herring, mackerel and other fish in the Pacific Ocean. Those fish are eaten not only by millions of people every year, but also by a wide variety of other sea creatures, from whales to dolphins to sea lions.

If the trend continues, climate change scientists say, it will imperil the ocean environment.

While researchers have sometimes connected weather extremes to man-made global warming, usually it’s not done in real time. Now a study is asserting a link between climate change and both the intensifying California drought and the polar vortex blamed for a harsh winter that mercifully has just ended in many places.

The Utah State University scientists involved in the study say they hope what they found can help them predict the next big weird winter.

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The United States just came out of a two-faced winter — bitter cold and snowy in the Midwest and East, warm and severely dry in the West. The latest U.S. drought monitor says 100 percent of California is in an official drought.

The new study blames an unusual “dipole,” a combination of a strong Western high pressure ridge and deep Great Lakes low pressure trough. That dipole is linked to a recently found precursor to El Nino, the world-weather changing phenomenon. And that precursor itself seems amplified by a build-up of heat-trapping greenhouse gases, the study says.

Vast stretches of the Somerset Levels, an expanse of coastal plains and wetlands in southwest England, have spent much of the winter underwater. At the peak of the crisis, some 11,500 hectares (28,420 acres) was submerged as violent storms brought “biblical” deluges week after week, for months on end. Along Britain’s scenic coastline, 80 mph gales and tidal surges have left cliffs crumbling into the rough sea, beaches and sand dunes eroded, sea defenses breached, and shorelines and harbors damaged beyond recognition.

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All along the coast of the U.K. and in other coastal communities around the world, the threat of sea level rise and more violent storms is forcing towns and governments to make difficult choices — build higher, build stronger, or retreat. In the U.S., both strategies are being explored. Famous for its levy system, New Orleans is now also incorporating open spaces designed to flood into city planning, following designs pioneered by the Dutch. For its part, much of the New Jersey coast, devastated by Superstorm Sandy, is choosing to rely almost entirely on bigger artificial sand dunes to hold the ocean back as towns attempt to rebuild right where they were before the hurricane hit.

The U.K.’s Environment Agency is experimenting with a kind of coordinated retreat for the hardest to defend coastal areas, a tactic referred to as managed coastal realignment. It’s a controversial approach for a relatively small island nation. But the recent wild winter storms are starting to change attitudes — strategic surrender suddenly seems like it may be the smart, sustainable solution.